1.4 Heat Transfer, Specific Heat, and Calorimetry
3 min read•june 24, 2024
Heat transfer is all about energy moving between objects due to temperature differences. It happens through , , and until everything reaches the same temperature. Understanding these processes is key to grasping thermodynamics.
tells us how much energy it takes to change an object's temperature. We use this to calculate energy transfers and temperature changes in various scenarios. It's a crucial concept for understanding how materials behave when heated or cooled.
Heat Transfer and Specific Heat
Heat transfer between objects
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- Heat transfers from higher to lower temperature objects until is reached where both objects have the same temperature
- transfers heat through direct contact in solids, liquids, and gases at a rate dependent on the material's (metals vs insulators)
- transfers heat through fluid movement due to density differences caused by temperature variations (hot air rising, cold air sinking)
- Radiation transfers heat through without requiring a medium and can occur in a vacuum with emission and absorption dependent on the object's temperature and surface properties (Sun's radiation, cameras)
- The rate of heat transfer is influenced by , which measures a material's ability to resist heat flow
Calculations with specific heat capacity
- Specific quantifies the heat required to raise the temperature of 1 gram of a substance by 1°C, measured in or and varies for different substances (water vs metal)
- Change in thermal energy relates to mass , specific heat capacity , and change in temperature by
- Calculate temperature change by rearranging to (heating water on a stove)
- Calculate energy required for a given temperature change using (energy to boil water)
- Heat capacity, the product of mass and specific heat capacity, represents the total amount of heat needed to change an object's temperature by 1°C
Thermal properties of materials
- is the energy required for a substance to change phase without changing temperature
- describes how materials change size or volume in response to temperature changes
- measures how quickly heat spreads through a material, combining , density, and specific heat capacity
Calorimetry and Energy Conservation
Energy conservation in calorimetry
- measures heat transfer during physical and chemical processes (mixing substances, )
- Energy conservation states energy cannot be created or destroyed, only transferred or converted, so total energy remains constant in a closed system with heat lost by one object equaling heat gained by another
- Solve calorimetry problems using these steps:
- Identify objects involved in heat transfer
- Determine heat flow direction from higher to lower temperature
- Apply energy conservation
- Use specific heat equation for each object
- Solve for unknown variable (final temperature, mass, specific heat capacity)
- Common calorimetry scenarios include:
- Mixing substances at different temperatures (hot and cold water)
- Heating or cooling a substance with an external source or sink (ice in a drink)
- Phase changes at constant temperature (melting ice, water)
Key Terms to Review (44)
Boiling: Boiling is the process of transforming a liquid into a gas, specifically when the liquid reaches its boiling point temperature and bubbles form throughout the liquid, causing it to rapidly vaporize. This phase change from liquid to gas is a fundamental concept in the study of heat transfer, specific heat, and calorimetry.
C: The specific heat capacity, or simply specific heat, is a measure of the amount of energy required to raise the temperature of a substance by one degree. It is a fundamental property of materials that describes their ability to store thermal energy and is a crucial concept in the study of heat transfer, calorimetry, and thermodynamics.
Calorie: A calorie is a unit of energy defined as the amount of heat required to raise the temperature of 1 gram of water by 1 degree Celsius. In scientific contexts, it is often replaced by the joule, where 1 calorie equals approximately 4.184 joules.
Calorie: A calorie is a unit of measurement that quantifies the amount of energy contained in food or the amount of energy required to raise the temperature of one gram of water by one degree Celsius. It is a fundamental concept in the study of heat transfer, specific heat, and calorimetry.
Calorimeter: A calorimeter is a device used to measure the amount of heat transferred to or from an object, often during chemical reactions or physical changes. It typically consists of an insulated container that minimizes heat exchange with the environment.
Calorimetry: Calorimetry is the experimental technique used to measure the amount of heat absorbed or released during a physical, chemical, or biological process. It is a fundamental concept in understanding heat transfer, specific heat, and phase changes in thermodynamics.
Conduction: Conduction is the transfer of heat through a material without any movement of the material itself. It occurs due to the collision and diffusion of particles within the substance.
Conduction: Conduction is the transfer of thermal energy through a material without the involvement of any bulk motion of the material. It occurs when heat flows from a region of higher temperature to a region of lower temperature within a material or between materials in direct contact, due to the kinetic energy of vibrating atoms and free electrons.
Constant-volume gas thermometer: A constant-volume gas thermometer measures temperature by observing the pressure of a gas held at constant volume. The relationship between pressure and temperature is governed by the ideal gas law.
Convection: Convection is the transfer of heat through the movement of fluids (liquids or gases) caused by temperature differences. It involves the physical motion of the fluid, carrying energy from one place to another.
Convection: Convection is a mode of heat transfer that involves the movement of a fluid, such as air or water, to transport thermal energy from one location to another. It is a crucial mechanism in the exchange of heat between a solid surface and a fluid in motion.
Debye: A Debye is a unit of electric dipole moment. It is commonly used to express the magnitude of molecular electric dipole moments and equals approximately $3.336 \times 10^{-30}$ Coulomb-meter.
Debye temperature: The Debye temperature is a characteristic temperature that indicates the temperature below which the specific heat capacity of a solid approaches zero. It is derived from the Debye model, which describes the phonon contribution to the specific heat in a solid.
Electromagnetic Waves: Electromagnetic waves are a type of energy that travels through space or a medium in the form of oscillating electric and magnetic fields. These waves are responsible for various phenomena, including heat transfer, magnetism, and the propagation of electric fields, and are fundamental to our understanding of Maxwell's equations and the electromagnetic spectrum.
First law of thermodynamics: The First Law of Thermodynamics states that energy cannot be created or destroyed in an isolated system, only transformed from one form to another. It is also known as the law of energy conservation.
First Law of Thermodynamics: The First Law of Thermodynamics states that energy can be transformed from one form to another, but it cannot be created or destroyed. It establishes the fundamental principle of energy conservation, which is crucial for understanding heat transfer, thermodynamic systems, and adiabatic processes in an ideal gas.
Heat Capacity: Heat capacity is a physical property that describes the amount of heat required to raise the temperature of a substance by a certain amount. It represents the material's ability to store thermal energy and is an important concept in understanding heat transfer, thermodynamics, and the behavior of materials under different temperature conditions.
Infrared: Infrared is a type of electromagnetic radiation with wavelengths longer than those of visible light, but shorter than those of radio waves. It is a form of thermal radiation that is invisible to the human eye, but can be detected as heat by the skin and specialized sensors.
Infrared radiation: Infrared radiation is a type of electromagnetic radiation with wavelengths longer than visible light but shorter than microwaves, ranging from approximately 700 nm to 1 mm. It is commonly associated with thermal radiation emitted by objects due to their temperature.
Isothermal expansion: Isothermal expansion is a thermodynamic process in which a gas expands at a constant temperature. During this process, the internal energy of the gas remains unchanged while work is done by the gas.
J/(g·°C): J/(g·°C) is a unit used to measure specific heat capacity, which is the amount of energy required to raise the temperature of a substance by one degree Celsius per unit mass. This unit is commonly used in the contexts of heat transfer, specific heat, and calorimetry to quantify the thermal properties of materials and understand energy exchange processes.
J/(kg·K): J/(kg·K) is a unit that represents the specific heat capacity of a material, which is a measure of the amount of energy required to raise the temperature of a unit mass of a substance by one degree Kelvin. This unit is commonly used in the context of heat transfer, specific heat, and calorimetry to quantify the thermal properties of materials and understand how they interact with energy.
Joule: The joule (J) is the fundamental unit of energy in the International System of Units (SI). It represents the amount of work done or energy expended when a force of one newton acts through a distance of one meter. The joule is a versatile unit that can be used to quantify various forms of energy, including thermal, electrical, and mechanical energy.
Kilocalorie: A kilocalorie (kcal) is a unit of energy commonly used in the field of thermodynamics. It is defined as the amount of heat required to raise the temperature of one kilogram of water by one degree Celsius.
Latent Heat: Latent heat refers to the energy released or absorbed by a substance during a phase change, such as the transition from a solid to a liquid or from a liquid to a gas, without a change in temperature. It is the energy required to change the state of a substance without altering its temperature.
Latent heat coefficient: The latent heat coefficient is the amount of heat energy required to change the phase of a unit mass of a substance without changing its temperature. It is typically measured in units of J/kg.
Mechanical equivalent of heat: The mechanical equivalent of heat is the amount of mechanical work needed to produce an equivalent amount of heat. It establishes a relationship between energy units used in mechanics and those used in thermal energy.
Molar heat capacity at constant volume: Molar heat capacity at constant volume ($C_V$) is the amount of heat required to raise the temperature of one mole of a substance by 1 degree Celsius at constant volume. It is a key parameter in understanding the thermodynamic properties of gases.
Phase Changes: Phase changes refer to the transitions between the different physical states of matter, such as solid, liquid, and gas. These changes occur when the energy input or output causes a substance to move from one state to another, altering its molecular structure and properties.
Q: Q, in the context of heat transfer, specific heat, and calorimetry, is a symbol used to represent the amount of thermal energy or heat that is transferred or exchanged between a system and its surroundings. It is a fundamental quantity in understanding the principles of thermodynamics and the behavior of heat-related phenomena.
Radiation: Radiation refers to the emission or transmission of energy in the form of waves or particles through space or a medium. It is a fundamental mechanism of heat transfer that plays a crucial role in the topics of heat transfer, specific heat, calorimetry, and the mechanisms of heat transfer.
Specific heat capacity: Specific heat capacity is the amount of heat energy required to raise the temperature of one unit mass of a substance by one degree Celsius (or one Kelvin). It plays a crucial role in understanding how different materials respond to heat and is key in processes like heat transfer, calorimetry, and thermodynamics.
State variable: A state variable is a property of a system that depends only on the current state of the system, not on how that state was reached. Examples include temperature, pressure, and volume.
Stefan-Boltzmann Law: The Stefan-Boltzmann law describes the total amount of energy radiated per unit surface area of a black body in unit time. It is a fundamental principle in the field of thermal radiation and is crucial for understanding heat transfer processes.
Thermal conductivity: Thermal conductivity is a material's ability to conduct heat. It quantifies the rate at which heat energy passes through a material given a temperature gradient.
Thermal Conductivity: Thermal conductivity is a material property that describes the ability of a substance to transfer heat. It is a measure of how quickly heat can flow through a material, and it is a crucial factor in understanding heat transfer processes.
Thermal Diffusivity: Thermal diffusivity is a material property that describes the rate at which heat can diffuse or spread through a material. It is a measure of how quickly a material can conduct heat and reach thermal equilibrium with its surroundings. This property is crucial in understanding heat transfer processes and the behavior of materials in various thermal applications.
Thermal Energy: Thermal energy is the total kinetic energy of the random motion of the particles (atoms and molecules) within a substance. It is a form of internal energy that is directly related to the temperature of a material and the heat transfer processes that occur within it.
Thermal equilibrium: Thermal equilibrium is the state in which two or more objects in thermal contact no longer exchange heat, resulting in a uniform temperature throughout the system. This occurs when the temperatures of the objects are equal.
Thermal Equilibrium: Thermal equilibrium is a state in which two or more objects or systems have reached the same temperature and no longer exchange heat energy. This concept is fundamental to understanding temperature, thermometers, heat transfer, and the behavior of thermodynamic systems.
Thermal Expansion: Thermal expansion is the phenomenon where the size or volume of an object increases as its temperature rises. This occurs because the atoms or molecules within the object vibrate more and occupy a larger space as they gain kinetic energy from the increased temperature.
Thermal Resistance: Thermal resistance is a measure of a material's ability to resist the flow of heat. It quantifies how effectively a material or system impedes the transfer of thermal energy from a hotter region to a cooler one, and is an important concept in the study of heat transfer, specific heat, and calorimetry.
Thermometer: A thermometer is a device used to measure and indicate the temperature of a substance or environment. It is a fundamental tool in the study of temperature and thermal equilibrium, heat transfer, and mechanisms of heat transfer.
ΔT: ΔT, or delta T, represents the change in temperature between two points or states. It is a fundamental concept in the study of heat transfer, specific heat, and calorimetry, as it quantifies the temperature difference that drives the flow of thermal energy.